Of course, thicker might mean gooder considering it's a uni-body and all, and it will take longer to rust through too!

But 18 gauge will be easier to work into shape by hand, for sure. I'm not sure what they're providing in today's repop is what was used originally. To me, most panels I've installed seemed to be thinner than what was originally used. That might simply be because the presses Ford had to stamp them out were massive and could handle stamping out an entire floor in one shot. Maybe pop out a rubber plug in a section of good floor and mic a section of it.